Well, two of my personal favourites are the fairly obscure Ansem Retort [http://ansemretort.org/ansemretort/index.html?comic=1] (a sprite comic, and one of the funniest things I've ever read) and Cuanta Vida [http://tf2.skyscrapersoup.com/?p=3] (a TF2 fancomic with some of the most interesting characters and interactions I've come across). Of course, for a more mainstream answer, I'll have to go with Homestuck [http://www.mspaintadventures.com/?s=6] (not only an incredible undertaking, with the author updating, on average, 5.5 panels a day, every day, but also one of the best examples of characterization, humour and badassery on the net, with certain [http://www.mspaintadventures.com/?s=6&p=003049] animated [http://www.mspaintadventures.com/?s=6&p=002779] segments [http://www.mspaintadventures.com/?s=6&p=002736] in particular bringing tears of awesome to my eyes. You do have to work past a fairly slow first act, though).